Wartime Radar Applications

World War II Klystron

This example, a CV35, didn't help to win as it's still in its original box!

The klystron and magnetron were developed in great secrecy during the early years of the war and enabled Britain to produce static, shipbourne and airborne radar equipments to defeat the Luftwaffe and the U-Boat menace.

John Higton e-mailed me to say that he thinks this valve was used in the Naval type 271 radar which was eventually developed into the RAF Type 13 and 14 radars.

And here's a couple undressed:

On the left a CV35 like that above but without its waveguide attachment

And on the right another marked "CV67"

Another World War II Radar Valve

As you can see it's a "CFT-15-E" and it's a triode with a directly heated filament. From the short leads it must have been designed for VHF operation.

According to www.electricstuff.co.uk it's a 5KW 600MHz triode pulsed radar valve used in WWII bombers.

What was the radar and was it used exclusively in U.S. aircraft? Does anyone know?

The box is dated August 14 1943 and measures about 3.5" cube

RF Power Oscillator

This VTR135, having an International Octal base, was originally supplied to the RAF and I believe is equivalent to the DET20 and is classed as a small transmitting valve. Output power is over 4 watts at 50 MHz although it can be used at lesser powers up to its maximum rating of 300 MHz. It has a big brother of similar appearance, the DET19, which is a twin triode used as a push-pull output valve for higher powers. Below is a similar valve carrying the code CV6 which is a "joint service number" for the DET20.

Several methods were adopted to minimise the grid-anode capacity coupled with reduced in-built inductance. This example uses the simple expedient of two top caps. The valve was designed specifically for use with a tuned circuit connecting its anode and grid. By using silver plated wire a decent efficiency could be obtained at VHF.

Having recently purchased a WS No19, that's the wartime tank transceiver, I recalled where I'd seen this valve before. In the 19 set is a simple super-regenerative receiver which doubles as a transmitter. Output is around 230 to 240 Mc/s. It was used for local tank to tank communications and officially had a range of about 1000 yards.

On the left is a bird's eye view of the compartment containing the valve.

It may also have been used in other equipment. Anyone any ideas?

Pete Dewar tells me he remembers the twin horned triode being used in an early type of IFF transmitter located in the tail of the Gloster Meteor. This piece of kit was an electro-mechanical version used prior to the crypto people getting involved. I wonder if Ferranti in Manchester produced it?

Other valves used in early VHF communications equipment, albeit having a lower power rating were the acorn valves, the 955, 956, 957 and 958 which I used to buy in the 1950's for a few shillings to build small super-regenerative VHF receivers for listening to transmissions from the local airport. These valves, of which all my examples unfortunately bit the dust years ago were tiny things no more than an inch or so in height.

The smallest valves were made near the end of the valve era. These were the "nuvistor" types which were much the same physical size as some transistors around at the time they were in use. The nuvistor had a good spec at UHF and was often used as a front end in sensitive receivers. In fact their performance was far superior to that of transistors until the advent of semiconductor devices with gain bandwidth products measured in GHz.